1. Field of the Invention
This invention relates generally to the field of disc drives and more particularly, but not by way of limitation, to an improved apparatus for reducing acoustic noise in disc drives.
2. Brief Description of the Prior Art
Disc drives of the type known as "Winchester" disc drives are well known in the industry. The archetype Winchester disc drives incorporated discs fourteen inches in diameter and were intended for use with large mainframe types of computers installed in specially constructed computer rooms in which such environmental elements as temperature and humidity were optimized for equipment operation. The users of such a system were typically located in locations far removed from the system itself and communicated with the system using keyboards and CRT displays called, appropriately enough, remote terminals. Since with such an arrangement only system maintenance and support personnel were commonly required to work directly within the computer room itself, little consideration was given to acoustic noise generated by such system elements as cooling fans and disc drive motors.
However, with the advent of personal computers, commonly located within office environments, acoustic noise generation has become a significant consideration in system design. Indeed, in some marketplaces, particularly Europe, the amount of allowable acoustic noise in the workplace is strictly controlled by regulatory agencies.
With such restrictions being placed on systems manufacturers, it has become common practice for manufacturers who expect to sell their products multinationally to analyze their intended market and specify their systems to meet the strictest requirements demanded in all target marketplaces.
Since most computer system manufacturers do not internally produce their own disc drives, but depend on specialized disc drive manufacturers, these system manufacturers have begun to strictly specify the amount of acoustic noise that the disc drive itself can contribute to the overall system.
In disc drives of the current technology, the major source of acoustic noise is sympathetic vibration of the disc drive housing caused by the spindle motor used to spin the discs or by the actuator used to move the read/write heads across the discs for data accesses. These disc drives are often in the form of a rectangular housing with a spindle motor and actuator motor mounted to the internal surface. Recent market demands for increased capacity, with accompanying increases in precision, have caused disc drive manufacturers to attach the shaft of the spindle motor and the pivot shaft of the rotary actuator motor to both the bottom and top plates of the disc drive housing. This has frequently resulted in housing surfaces vibrating at resonant frequencies that increase the total amount of acoustic noise.
Several approaches to acoustic noise reduction have been taken by disc drive manufacturers. Most of these involve the addition of compliant isolation devices between the noise source (the motors) and the external housing. However, such devices add expense to the design and require that space be set aside for them within the housing. With market trends toward increased capacity and smaller physical drive sizes, manufacturers have been understandably reluctant to allow room for these types of noise isolation devices in their designs.
Clearly, a need has arisen for an apparatus for reducing acoustic noise that does not add to manufacturing costs and also does not require additional space within a disc drive assembly.